The invention is applicable to the embodiment of two types of magnetic heads, namely flying heads for disk storage systems, or contact heads for tape storage systems.
The document relating to the U.S. Pat. No. 4,949,207 describes a method for embodying a thin-filmed and magnetic head with a planar structure. The head obtained by means of this method is shown in a cutaway view on the accompanying FIG. 1. It includes a substrate 10 in which a first caisson has been filled up by a first magnetic film 16 obtained via electrolytic growth on an electrode 14, a winding 20 embedded in a nonconducting film 18, two magnetic blocks 23, 24, a second magnetic film forming two flux concentrators 30, 31, a central nonconducting islet 32, a nonconducting film 34, such as a silica film, defining another caisson which has been filled up with another magnetic film, also formed by electrolytic growth, this film being separated into two portions 46, 48 by a non-magnetic spacer 42 constituting the gap of the head.
A similar head may be obtained by suppressing the flux concentrators 30 and 31 and by ensuring that the upper film 46, 48 takes support directly on the blocks 23, 24.
In the remainder of this document, the magnetic portion disposed on both sides of the spacer 42 shall be denoted by the term the "upper polar piece", the lower polar piece being the one corresponding to the magnetic film 16.
In this prior technique, the upper polar piece is thus obtained by electrolytic depositing. A magnetic material suitable for this technique may be an iron-nickel alloy, namely a soft material, with a composition of 80/20.
Although providing satisfaction in certain respects, this technique does exhibit a certain number of drawbacks. In fact, the choice of a magnetic material able to be electrolytically deposited is relatively limited, and the iron-nickel alloy is in the last analysis one of the rare materials which is suitable. Now, this material does not offer all the qualities required, especially as it exhibits a relatively slight mechanical hardness (Vicker's hardness of about 100). This weakness virtually renders this technique unable to produce contact heads owing to the rapid wear which accordingly would occur in such contact heads. In addition, the magnetic materials conventionally used and which are able to be electrolyzed do not exhibit optimal magnetic characteristics (saturated magnetization, magnetic permeability, etc).
Of course, there are other magnetic materials presenting better hardness and/or magnetic characteristics, but these materials are not suitable for electrolytic deposition and need to be treated by cathodic evaporation, for example. However, in this case, it is extremely difficult to obtain a homogeneous and particularly thick magnetic film on both sides of the gap, this being the case with the electrolytic technique.